Adhesive for processing a microelectronic substrate, and related methods

ABSTRACT

Described are methods for processing microelectronic device substrates by a lapping step, e.g., a final lapping step, wherein the step includes the use of an elastomeric pressure-sensitive adhesive to secure the microelectronic device substrate to a carrier that holds the substrate to a surface of the carrier during the lapping step, and wherein the pressure-sensitive adhesive can be a non-polysilicone based adhesive having mechanical properties that include a tan delta that is below about 0.2.

FIELD OF THE INVENTION

This invention relates to methods for processing microelectronic devicesubstrates by what is referred to in the microelectronic device arts asa lapping step, e.g., a final lapping step which is sometimes alsoreferred to as an “Actuated Kiss lap process” (“AKL”) or a “finalpolishing step,” wherein the step includes the use of an elastomericpressure-sensitive adhesive to secure the microelectronic devicesubstrate to a carrier that holds the substrate to a surface of thecarrier during the lapping step.

BACKGROUND

Many types of microelectronic devices or precursors of microelectronicdevices are prepared by methods that include a “lapping” process, whichis a step or series of steps of abrading a surface of the device orprecursor (i.e., a “substrate”) to remove material from the surface.Material may be removed for one or more of: preparing a flat(planarized) surface; producing a desired feature height or “depth” atone area of the surface; producing a desired shape of the surface; orfor a combination of these different purposes. The type ofmicroelectronic device or precursor being processed will vary and mayinclude devices and precursors such as integrated circuits, opticaldevices, and magnetic read and read-write heads that include a slider.

A specific example of a type of microelectronic device that is commonlyprepared by steps that include lapping is a “slider assembly”(alternately referred to as a “head assembly”) for use in a hard diskdrive system. Hard disk drive systems (HDDs) include one or moremagnetic data storage disks. A transducing head carried by a sliderassembly near the disk, while the disk spins, is used to read from orwrite to data tracks on the magnetic disk. The slider assembly includesa transducing read head, a transducing write head, or both, along with a“slider element” that includes a surface that faces the spinning diskand acts as an “air bearing” relative to the spinning disk. During use,the slider assembly is carried at a location very close to the spinningdisk surface, but not in contact with the disk surface. The transducing(read or write) head must be suspended or “fly” over the spinning disksurface at a predetermined head-to-disk spacing. To maintain aconsistent distance between the rotating disk and the head assembly, thesurface of the slider element is shaped to create a layer of airin-between the rotating disk surface and the suspended head assembly.The layer of air produces an aerodynamic force against the head assemblyso as to urge the head assembly away from the surface of the rotatingdisk. A load force provided by a flexure or spring that carries the headassembly opposes the aerodynamic force, and the resultant of the twoopposing forces determines the flying height of the head assembly.

A slider assembly, including one or more transducing heads and theslider element, is typically produced by using thin film depositiontechniques also used to produce many other microelectronic devices. In atypical process, an array of slider assemblies is formed on a commonsubstrate or wafer. Each slider assembly contains at least onetransducing head, as well as a slider element having a surface on oneside of the slider assembly. After forming the wafer to contain a largenumber of slider assemblies, the wafer is sliced into a number of groupsof connected slider assemblies for further processing. By some methods,rows or “bars” (“slider bars”) of slider assemblies are cut from thewafer, with each slider bar having a number (e.g., seventy) of sliderassemblies connected in a side-by-side pattern on each bar.

Typically, the slider bars (containing multiple, connected sliderassemblies) are processed by a lapping step. The lapping step processesthe surfaces of the slider assemblies to remove a small or minute amountof material from each slider assembly surface to result in a desiredthickness or depth (referred to as the “stripe height”) between thatsurface and one or more transducer heads of the slider assembly, whichare located adjacent to and below that surface. Lapping is alsoperformed and can be effective to remove material from the sliderelement of slider assemblies, to produce a desired surface shape.

To carry out the lapping process, a microelectronic device substrate(e.g., a slider bar) is secured to a carrier, and the carrier is used tohold a surface of the substrate against a moving abrasive material, witha light amount of pressure. Contacting the surface of the substrate withthe abrasive material, with relative motion between the surface and theabrasive material, is effective to remove small or minute amounts ofmaterial from the surface of the substrate. A lubricant such as mineraloil is also normally present at the interface between the substratesurface and the moving abrasive material. The substrate is commonlysecured to a surface of the carrier by a pressure-sensitive adhesive,which must exhibit certain specific performance requirements to beuseful for this purpose, such as generally providing a secure engagementbetween a surface of substrate and a surface of the carrier, even in thepresence of a lubricant.

Industry standard adhesives for securing a microelectronic devicesubstrate to a carrier for a lapping step include silicone-based(polymeric silicone-based, e.g., polydimethylsiloxane)pressure-sensitive adhesives. But silicone-based adhesives havedisadvantages in that they tend to swell or leach during processing,e.g., in the presence of certain lubricants used in lapping processes,which causes contamination of a substrate that is being processed by thelapping step, of the lapping equipment, or both. Silicone can be highlyproblematic if present as a contaminant of a microelectronic device,even if present at only a very tiny amount. Unlike organic contaminants,silicone cannot be oxidized by atomic oxygen. If oxidization of asilicone contaminant at a substrate surface is attempted, a glassysilicate, which is very difficult to remove, will be formed and willremain at the surface. Silicones, being useful as release agents, alsocause great difficulties in trying to bond an applied layer of materialto a surface that is contaminated with a silicone; as an example, ifmetallization is attempted on a surface that is contaminated withsilicone, adhesion is greatly diminished. Silicone contamination ofmagnetic and chemical sensors can be highly problematic; evenparts-per-million amounts of silicone present on a surface of a sensorcan dramatically and quickly impede performance of the sensor. Minimalexposure of a hard disk read-write head to silicone can result in errorsor drive failure.

As a general matter, an improvement in any aspect of the variousprocesses used to produce microelectronic devices will always bedesired. With more specific regard to lapping steps, the Applicant hasnow discovered that certain types of non-silicone-basedpressure-sensitive adhesives can be successfully used to secure amicroelectronic device substrate to a carrier, with useful oradvantageous results. This discovery will allow for the elimination ofthe negative effects that result from using standard silicone-basedadhesives in lapping steps.

SUMMARY

The invention relates to methods for processing microelectronic devicesubstrates by what is referred to in the microelectronic device arts asa lapping step. Example methods of the invention more particularlyinvolve processing a microelectronic device substrate by a final lappingstep, also referred to as a “kiss lapping step” or a “polishing lappingstep.” The inventive lapping step uses a pressure-sensitive adhesive tosecure a microelectronic device substrate to a carrier, to hold thesubstrate to a surface of the carrier during the lapping step. Thepressure-sensitive adhesive is one that is not silicone-based and doesnot require any silicone-based adhesive material, and may containsubstantially or entirely only non-silicone-based materials such aspolyacrylate or polyurethane materials. Preferred adhesives also are notrequired to contain and can specifically exclude the presence of tin(e.g., as a catalyst material for certain adhesive polymers). Useful andpreferred pressure-sensitive adhesives of the invention exhibitmechanical properties and adhesive properties (see below) that have beenfound to provide especially desirable results in a final lapping stepwhen used to secure the substrate to the carrier surface.

A final lapping step can be designed to accomplish one or two importantobjectives. A first objective can be to remove an amount of materialfrom a surface of the substrate to produce a desired thickness of alayer of the surface material. A lapping step may be performed, forexample, to produce a desired thickness of layer of surface materialthat covers an underlying electronic feature, often as a transducer.Another possible objective is, by removal of the surface layer material,to produce a desired shape of a surface of the substrate, for example adesired shape of a surface of a slider element of a slider assembly.

The presently-described methods may be useful or even advantageous whenprocessing any type of microelectronic device substrate by a lappingstep. The substrate may be any microelectronic device or a precursorthereof that is produced using thin film deposition techniques toselectively deposit onto a substrate (e.g., wafer), and then remove,multiple layers of materials that will function as conductive,semiconductive, or insulating features of a microelectronic device. Thesubstrate may be ceramic, metal, or semiconducting material, etc. Thematerials that are selectively applied and removed to form thefunctioning microelectronic features may be metals, alloys, insulatingmaterials, semiconducting materials, etc.

Types of microelectronic devices prepared in this manner include devicesthat contain integrated circuits, optical devices, or transducer heads(magnetic read and read-write heads, among others. Many details of thepresent description are presented in terms of a lapping step forprocessing a microelectronic device substrate that is a “slider bar,”meaning a bar of multiple slider assemblies that are connected at theirlength-wise edges. While the present description is presented in largepart as applying to lapping steps for processing slider assemblies, theinvention, including the use of a pressure-sensitive adhesive asdescribed herein, is not limited to a lapping process or lapping stepthat operates on a slider assembly as the substrate. Instead, whileslider assemblies (and, more particularly a slider bar) are exemplarysubstrates, inventive lapping steps as described can be used with anytype of microelectronic device substrate that can be processed in auseful manner by a lapping step, including microelectronic devicesubstrates that are different from slider assemblies and slider bars,including devices and their precursors that are designed to function asoptical devices, memory devices, integrated circuits, among others.

For use with a microelectronic device substrate (or just “substrate,”for short) that is a slider bar that includes one or more sliderassemblies, a lapping step as described can have a purpose of removing avery precise and typically very small amount of material from a surfaceof the substrate that covers one or more transducer heads, e.g., a readhead, a write head, or (typically) both. The lapping step is performedto remove an amount of material from a surface of the slider assembly(an amount of “surface layer material”) that is located between theslider assembly surface and the one or more transducer heads. The amountof material removed is an amount that will result in a desired thicknessof that surface layer material remaining between the surface and the oneor more transducer heads at the end of the lapping step. The amount ofthat material left to remain after the lapping step, based on thickness,is referred to as “stripe height,” and is an amount that results indesired performance of the transducer heads when the slider assemblyfunctions as part of a slider assembly (a.k.a., “head assembly”) of ahard magnetic disk drive. The amount of the surface layer material thatis removed from a slider bar as a substrate to produce a desired stripeheight of slider assemblies of the slider bar can be measuredelectronically during the a kiss lapping process, and is typically lessthan about 100 nanometers.

As another objective of a lapping step for processing a microelectronicdevice substrate that is a slider bar or that includes one or moreslider assemblies, the lapping step can be performed to produce adesired surface shape of a slider element of the slider assembly. Theslider element of a slide assembly includes a surface that, during useof the slider assembly in a hard disk drive, faces a surface of aspinning hard drive magnetic disk. The slider element surface acts as anair bearing that holds the slider assembly, including its transducerhead or heads, at a desired height relative to the spinning surface ofthe magnetic hard drive disk. During a lapping step, especially a finallapping step (a “polishing lapping step” or a “kiss lapping step”), thatsurface of the slider element that will face the spinning disk surfaceduring use can be specially shaped so that it will properly function asan air bearing. This shaping of the slider assembly surface during akiss lapping step can be referred to as global shaping of the surface.

The invention relates to the novel and inventive uses of certain typesof elastomeric, pressure-sensitive adhesives in a lapping step to securea microelectronic device substrate to a carrier, during lapping.According to the invention, certain specific physical and adhesionproperties have been identified as being useful or preferred in apressure-sensitive adhesive used for holding the microelectronic devicesubstrate at the surface of a carrier, especially during a kiss lappingstep. These properties include, alone or in combination: desiredelasticity and flow properties including elastic modulus, loss modulus,and “tan delta”; peel force as measured in a shear direction; tack; andchemical resistance to lubricant materials used in a lapping step suchas mineral oil.

According to the present description, the term “pressure-sensitiveadhesive” (PSA) is used as that term is generally used and understood inthe chemical and adhesive arts, to describe materials that areinherently tacky or, by the addition of tackifying resins (“tackifiers”)are formulated to be tacky, meaning sticky to the touch at a surface.Examples of materials that are classified as pressure-sensitiveadhesives are described in D. Satas, Handbook of Pressure-sensitiveadhesives, 2^(nd) edition, page 172, 1989.

In a kiss lapping process a carrier is used to hold a microelectronicdevice substrate, and to handle the substrate to place the substrate incontact with a moving (e.g. rotating) abrasive material, at a desiredpressure, for an amount of time that is effective to remove a desiredamount of material from the surface of the substrate that is held incontact with the moving abrasive (sometimes referred to herein as the“contacted surface”). During lapping, as the substrate is held incontact with the moving abrasive material, and surface layer material isremoved from the contacted surface, frictional forces are placed on thesurface of the substrate that contacts the abrasive. The forces willremove material from the contacted surface and will also produce a forceat the contacted surface in a direction of movement of the abrasivematerial relative to the contacted surface, i.e., along the contactedsurface in a direction from the “forward end” to a “trailing end” of thesurface. This force will cause an amount of torque to be produced on thesubstrate, causing the leading end to be drawn toward the abrasivematerial. That torque can, in turn, become applied to thepressure-sensitive adhesive that holds the opposite (“non-contacted”)surface of the substrate to the carrier. Depending on the mechanicalproperties of the adhesive, e.g., elasticity and flow properties asmeasured by modulus and tan delta, the adhesive may be capable ofallowing or preventing useful lapping of the substrate in the presenceof the applied torque. More specifically with respect to lapping aslider assembly or slider bar, mechanical properties of thepressure-sensitive adhesive will affect the amount of material that isremoved from a surface of a slider element portion of a slider assemblysubstrate, especially at and toward the leading end of the substrate,thus affecting the global shaping of the slider element.

Accordingly, mechanical properties, as well as adhesive properties of anadhesive used in a lapping step can be of high importance, with certainproperties now being identified as particularly desired for the adhesiveto perform well as a lapping adhesive. These properties include theelasticity of the adhesive (modulus) and the “tan delta,” which isrelated to elasticity (e.g., elastic modulus). Also important is theadhesive peel strength (peel force, e.g., measured in a shear direction)of the adhesive. In addition to these mechanical and adhesionproperties, the adhesive must be sufficiently resistant to chemicalmaterials that are also present in a lapping step, one common materialbeing mineral oil, used as a lubricant. Resistance to mineral oil meansthat the adhesive does not degrade in the presence of mineral oil, andis dimensionally stable in the presence of mineral oil, at least todegrees that are sufficient for the adhesive to be useful in a lappingstep as described.

An important mechanical property of a lapping adhesive is elasticitymeasured as elastic modulus (G′ or “storage modulus”), which relates tothe flexibility of the adhesive. Flexibility of the adhesive allows formovement (deformation) of the adhesive while the adhesive holds thesubstrate onto a surface of a carrier while the substrate contacts amoving abrasive material during lapping. Depending on its elasticity,the adhesive will allow for a greater or a lesser amount of movement,e.g., twisting (about an axis extending along a length (the longestdimension) of a slider bar substrate) of the substrate in response tothe torque applied to the substrate by the abrasive material movingagainst the contacted surface. A greater or lesser elasticity of theadhesive will allow for more or less twisting of the substrate,resulting in either a greater or a lesser amount of material beingremoved from the substrate, especially at a forward end of thesubstrate, and a greater or a lesser degree of global shaping of thesubstrate being produced during lapping. Loss modulus (G″) is anotherimportant mechanical property of the adhesive, and relates to flowproperties of the adhesive. Like the elastic modulus (“storagemodulus”), the loss modulus of the adhesive also affects the globalshaping of the substrate during lapping by allowing for more or lesstwisting of the substrate and a greater or a lesser amount of materialbeing removed from a leading end of the substrate.

Elastic modulus (or “storage modulus”) (G′) and loss modulus (G″) can beconsidered together as a single unit-less value known as “tan delta,”which is the unit-less value derived by dividing the loss modulus by thestorage modulus, i.e.: tan delta is the value of G″/G′. According tocertain preferred adhesives of the present description, a useful tandelta of the adhesive can be below about 0.2, e.g., in a range fromabout 0.05 to 0.2, such as in a range from about 0.08 to 1.5.

Peel force and tack are adhesive properties of pressure-sensitiveadhesives. The peel adhesion and tack should be sufficient to cause asubstrate to securely adhere to the adhesive, and consequently to asurface of a carrier, during lapping, without allowing for failureduring the lapping process, and also to allow for removal of thesubstrate from the carrier after a lapping step without causing damageto the substrate. If peel adhesion or tack is too low, a substrate suchas a slider bar may not adhere to the adhesive and to the carrier duringthe lapping step. If peel adhesion or tack is too high, the substrate(e.g., slider bar) may be difficult to remove from the adhesive and thecarrier following lapping, and the substrate may be damaged during itsremoval from the carrier. According to certain preferred adhesives ofthe present description, a useful peel force of the adhesive can be in arange from about 50 to 1000 grams (force), such as from about 70 to 500or from about 100 to 250 grams force.

Many past and presently-conventional pressure-sensitive adhesives usedin lapping steps are silicone-based, meaning adhesives that contain ahigh amount of silicone-based adhesive polymer such aspolydimethylsiloxane as the functioning adhesive. According to thepresent description, non-silicone-based pressure-sensitive adhesiveshave now been found to be useful and advantageous for use as a lappingadhesive as described, preferably including mechanical, adhesive, andchemical properties as described herein. Examples of suchnon-silicone-based adhesives include polyurethane-basedpressure-sensitive adhesives and polyacrylate pressure-sensitiveadhesives (meaning pressure-sensitive adhesives derived from acrylatemonomers, methacrylate monomers, or combinations thereof). Preferredadhesives as described can contain not more than a minor amount ofsilicone-based polymer, e.g., polydimethylsiloxane, or essentially nosilicone-based polymer, e.g., less than 5, 1, 0.5, or 0.1 weight percentsilicone-based polymer, based on total weight of the adhesive.

Many known and conventional polyurethane adhesives include tin used as acatalyst for a polymerization reaction to form polyurethane polymer ofthe adhesive. Tin, however, can be disfavored for industrial uses, suchas for uses in microelectronics manufacturing. According to theinvention, polyurethane pressure-sensitive adhesives that have beenidentified for use in a lapping process as described do not require andcan preferably exclude the use of tin as a catalyst, or for any otherpurpose in the adhesive. Preferred polyurethane pressure-sensitiveadhesives as described herein can be “free of tin,” which means that theadhesive can include a non-tin-containing catalyst (e.g., abismuth-based catalyst) and does not contain a tin-containing catalyst,or, alternately stated, can include less than 100 parts per million(ppm), e.g., less than 50, 10, 1, or 0.1 ppm tin, based on total weightof the adhesive.

In one aspect, the invention relates to a method of lapping amicroelectronic device substrate. The method includes providing acarrier and providing a pressure-sensitive adhesive film, and, in anyorder effective to secure the substrate to the carrier: placing thepressure-sensitive adhesive film on the carrier, and placing themicroelectronic device substrate in contact with the adhesive film. Themethod then includes lapping the microelectronic device substrate, whilethe substrate is secured to the carrier by the pressure-sensitiveadhesive. The adhesive film includes adhesive polymer and can optionallyand preferably have an elastic modulus in a range from 100 to 500kilopascals, a Tan Delta in a range from 0.05 to 0.2, or both.

In another aspect the invention relates to elastomeric adhesive filmcomprising adhesive polymer, the adhesive film being useful to adhere amicroelectronic device substrate to a carrier during a step of lapping asurface of the microelectronic substrate. The adhesive film canoptionally and preferably have mechanical properties that include anelastic modulus in a range from 100 to 500 kilopascals, a Tan Delta in arange from 0.05 to 0.2, or both.

In yet another aspect, the invention relates to a stack comprising anadhesive film of the present description in contact with a releaseliner, e.g., with the adhesive film of the stack having a thickness in arange from 14 to 21 mils.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of an adhesive product of the present description,the embodiment shown being a stack that contains a non-siliconepressure-sensitive adhesive as described along with other optionallayers.

FIG. 2 is a schematic side view of an embodiment of an exemplary lappingprocess.

FIG. 3 is a schematic side view of a carrier tool (“carrier” or “lappingcarrier”) that includes an adhesive as described and a substrate securedto the carrier by the adhesive.

The drawings are schematic and not to scale.

DETAILED DESCRIPTION

The invention as described herein relates to pressure-sensitiveadhesives that have now been identified as providing useful oradvantageous performance when used in methods of lapping microelectronicdevice substrates.

The substrate may be any type of microelectronic device that can beprocessed by lapping, with examples including microelectronic devicesubstrates that include integrated circuits, memory components, opticalcomponents, or a slider assembly (including a slider bar, or slider rowcontaining multiple slider assemblies), or a precursor of any of these.In a lapping step, an amount of material is removed from a surface ofthe substrate. The type of material may differ depending on thesubstrate. For a substrate that is a slider assembly or that containsmultiple slider assemblies, a surface layer may be made of a combinationof aluminum oxide (Al₂O₃) and titanium carbide (TiC).

In a lapping step, a holder or “carrier” of a lapping apparatus is usedto hold a microelectronic device substrate such as a slider bar incontact with a moving abrasive material. As the substrate is held incontact with the moving abrasive material, and as material is removedfrom the surface of the substrate that contacts the moving abrasive,frictional forces are produced on the contacted surface. The combinationof friction and movement between the abrasive material and the contactedsurface will produce a force on the substrate in the direction ofmovement of the abrasive material relative to the substrate. Torque isproduced on the substrate, causing the leading end (the end of thesubstrate that first comes into contact with the moving abrasivematerial) of the substrate to be drawn toward the abrasive material and,in turn, allowing for or causing a larger amount of surface layermaterial to be removed from the leading end of the substrate, therebyproducing a shaped surface having more material removed from the surfaceat the leading end relative to the trailing end. The amount and form ofthe shaping of the surface (global shaping) will be affected by themechanical properties of the adhesive, e.g., elasticity and flowproperties (cohesive strength), which will allow for more or lessmovement (twisting) of the substrate as a result of the torque. Whenprocessing a slider element by lapping, the mechanical properties of thepressure-sensitive adhesive, and their effects on the amount of materialthat is removed from the contacted surface at the leading end, which isthe location of the slider element portion of a slider assembly, therebyaffect the global shaping of the slider element.

To produce a slider assembly having controlled, useful, or advantageousshaping of the surface of the slider element, along with a desiredamount of removal of material from other portions of the sliderassembly, such as at the trailing end (measured by “stripe height”), ithas now been discovered that a pressure-sensitive adhesive that securesthe slider assembly to the carrier can have an elasticity, measured aselastic modulus (G′ or “storage modulus”), in a desired range. Apreferred elasticity will allow for a desired (e.g., controlled) amountof movement of the substrate relative to the carrier and the movingabrasive (i.e., twisting of the substrate about an axis of the substratethat is co-planar with the surface of the abrasive material, and that isperpendicular to the direction of relative motion between the substrateand the moving abrasive material) in response to the torque that isapplied to the substrate by the moving abrasive material contacting thecontacted surface. According to methods of the present invention,preferred storage modulus of a pressure-sensitive adhesive for use in alapping process, e.g., a kiss lapping step, can be in a range from about100 to about 500 kilopascals.

Along with the elastic modulus (“storage modulus”), the loss modulus(G″) of the adhesive also affects the removal of material from asubstrate surface during lapping, and influences the global shaping ofthe substrate by allowing for a greater or a lesser amount of materialto be removed from the leading end of the substrate due to controlledtwisting of the substrate relative to the carrier and the movingabrasive due to torque resulting from applied frictional forces. Theelastic modulus (or “storage modulus”) (G′) and loss modulus (G″) can beconsidered together as a single unit-less value known as “tan delta,”which is the ratio of loss modulus divided by storage modulus, G″/G′.According to preferred embodiments of the invention, preferred adhesivescan have a tan delta that does not exceed about 0.2, e.g., a tan deltain a range from 0.05 to 0.2.

Modulus, including both elastic modulus and loss modulus, can bemeasured by known techniques and using equipment that is known andcommercially available. One well-understood method for measuring modulusand related mechanical properties (e.g., tan delta) of elastomericadhesives is dynamic mechanical analysis (DMA), by use of a parallelplate rheometer (or oscillatory rheometer) programmed to characterizethe physical properties of a sample of adhesive. Various commercialrheometers are available from companies that include TA Instruments (NewCastle, Del., USA) and Anton Paar GmbH, Austria. According to thepresent description, elastic modulus, loss modulus, and tan delta, canbe measured, of a pressure-sensitive adhesive as described, by use of acommercially available rheometer (such as a Modular Compact RheometerMCR 302 from Anton Paar) using settings that include a temperature of 25degrees Celsius, a frequency of 10 hertz, an amplitude of 10 millirad,and a strain of 0.2 percent. For a “frequency sweep” test method whereinthe angle of oscillatory movement and the temperature are held constant,the frequency can be varied from 100 hertz to 0.1 hertz.

According to specific preferred adhesives as described, and methods oftheir use in lapping procedures, the modulus and tan delta of theadhesive can be within ranges specified herein when measured asdescribed, to provide the adhesive with mechanical (e.g., flow andelasticity) properties that are useful or especially effective in alapping step for processing a microelectronic substrate such as asubstrate that includes a slider assembly. Such mechanical propertieshave been identified as being particularly useful to provide flow andelasticity properties that result in a desired level of flexibility,resulting in a very slight amount of controlled movement of thesubstrate, especially twisting, relative to the carrier and the movingabrasive. Such slight controlled movement can result in a useful,desired, or advantageous degree and form of global shaping of a sliderelement surface of a slider assembly during kiss lapping. According tocertain particularly preferred pressure-sensitive adhesives nowdiscovered to be useful for providing these desired or improved effectsduring lapping, including polyurethane-based and polyacrylate-basedpressure-sensitive adhesives, an elastic modulus (storage modulus, G′)of the adhesive can be in a range from about 100 to about 500kilopascals, while the tan delta is below about 0.2, such as in a rangefrom about 0.05 to 0.2.

Another property of an adhesive that is important in a lapping processis peel adhesion or peel strength of the adhesive, which is a measure ofthe bond strength created, e.g., in a shear direction, between a surfaceof a substrate and a surface of the adhesive that contacts the surfaceof the substrate. According to certain preferred adhesives of thepresent description, in addition to an elastic modulus and a tan deltaas specified herein, particularly preferred adhesives can exhibit a peelforce of in a range from about 50 to 1000 grams (force), such as fromabout 70 to 500 or from about 100 to 250 grams force.

Peel force can be measured by known techniques and using equipment thatis known and commercially available. One well-understood method formeasuring peel force is by use of a shear tester apparatus, such as onesold under the trade name Dage, e.g., of the Dage 5000 series. Accordingto the present description, peel force of an adhesive as described canbe measured by this instrument or a similar instrument using a 5000kilogram (kg) (or 1000 kg) load cell, a 100 gram test load, a test speedof 25 microns per second, a shear height of 20 microns, and a BST-1.00Dage DWG test needle.

According to the invention, elastomeric pressure-sensitive adhesives forthe highly-sensitive final polishing step of a microelectronic devicesubstrate such as a slider assembly have been found to benefit from orto require a combination of very particular mechanical, adhesive, andchemical properties, including one or a combination of: elastic modulus,Tan Delta, peel strength, and dimensional stability (resistance tomineral oil). Industry standard adhesives are silicone-based (e.g.,polydimethylsiloxane). But silicone-based adhesives tend to swell orleach during processing, causing contamination of lapping equipment,substrates, or both. Previously, polyurethane and polyacrylate(including polymethacrylate) adhesives have not been successfullyformulated to be useful for securing a microelectronic device substrateto a carrier during a lapping step. According to the invention, usefuladhesives can be prepared substantially or entirely fromnon-silicone-based polymers such as polyacrylates (includingpolymethacrylates) and polyurethanes. Moreover, while many polyurethaneadhesives contain tin as a catalyst, which is not compatible withmicroelectronics processing, preferred polyurethane adhesives need notcontain tin as a catalyst, and may instead contain a bismuth-basedcatalyst, which is acceptable for microelectronic processing.

An adhesive as described (independent of polymer chemistry) can containminimal or no solvent, e.g., can contain one-hundred percent solids, andcan be non-foamed, with a low amount of bubbles or voids. For example,the adhesive can contain less than 5, 2, 1, or 0.5 weight percentsolvent and can contain substantially no bubbles or entrained gases,e.g., less than 5, 2, 1, or 0.5 percent gaseous bubbles by volume. Insome embodiments, he adhesive can contain a high amount of polyurethane,polyacrylate, or a combination of these materials as an adhesivematerial, with minor or no amounts of other adhesive materials ornon-adhesive additives. In these or other embodiments, additives such asa tackifier, plasticizer, or both may be present in a minor but usefulamount. Example adhesives can be substantially entirely polyurethane,polyacrylate, or a combination thereof, such as least 70, 80, 90, 95, or99 weight percent polyurethane, polyacrylate, or a combination thereof,based on total weight adhesive. These or other example adhesives can besubstantially entirely polyurethane, polyacrylate, or a combinationthereof with optional tackifier, plasticizer, or both, such as least 70,80, 90, 95, or 99 weight percent polyurethane, polyacrylate, or acombination thereof, and tackifier, plasticizer, or both.

Elastomeric polyurethane materials are known in the chemical, polymer,and adhesives arts and, according to the invention, can be used toprepare a polyurethane pressure-sensitive adhesive having mechanical(e.g., elastic and flow properties), adhesive, and chemical propertiesas described.

Polyurethanes are polymers composed of organic units joined by carbamate(urethane) links. Preferred polyurethane adhesives, being elastomeric,are also thermoplastic, meaning that the polymeric composition can bemelted and re-heated and re-formed.

Useful polyurethanes can be formed by reacting a polyisocyanate compoundwith a compound that has reactive hydrogens (e.g., hydroxide moieties)capable of reacting with the isocyanate groups, one example of such acompound being a polyol. The polyisocyanate compound can be adi-isocyanate monomer that can react directly with thereactive-hydrogen-containing compound (e.g., polyol, see below), or canbe a compound that is derived from pre-reacting di-isocyanate monomersto form a polyisocyanate compound that is an oligomer, pre-polymer, orpolymer, etc., of polyisocyanate (e.g., di-isocyanate) monomers.

Examples of preferred polyisocyanate monomers are di-isocyanate monomersthat contain two reactive isocyanate (NCO—) moieties. More specificexample are compounds that include two reactive isocyanate moietiesattached to a non-reactive aliphatic or a non-reactive aromatic compound(or “radical”). Some exemplary aromatic di-isocyanates monomers includediphenylmethane di-isocyanate (MDI) and toluene di-isocyanate (TDI).Some exemplary aliphatic di-isocyanate monomers include hexamethylenedi-isocyanate (HDI), isophorone di-isocyanate (IPDI), among others. Thepolyisocyanate monomer useful to prepare the polyurethane or apre-polymer or oligomer precursor can contain a high level ofdi-functional polyisocyanate monomers (as opposed to tri- or higherfunctionalities), e.g., exclusively di-functional monomers, such as atleast 90, 95, or 99 percent by weight di-functional isocyanate monomersbased on total weight polyisocyanate monomers, i.e., the averagefunctionality of the polyisocyanate monomer can be below 3, e.g., belowabout 2.5, 2.2, or 2.1.

The polyurethane polymer is prepared by the condensation reactionbetween the polyisocyanate and an active-hydrogen-containing materialsuch as a hydroxyl(-OH)-containing material, e.g., polyol. Preferably,di-isocyanate monomer or an oligomer, pre-polymer, or polymer thereof,can be combined and reacted with a material that includes multiplereactive hydrogens, such as a compound (e.g., monomer, oligomer,pre-polymer, polymer, etc.) that includes multiple (especially two)hydroxyl (—OH, or alcohol) moieties, especially a polyol, such as adiol, e.g., a polyether polyol.

A useful polyol can be any polyol that is capable of forming apolyurethane adhesive as described, having useful or preferredmechanical properties and adhesive properties, etc. The polyol can be ofany molecular weight that will be useful to react with thepolyisocyanate to provide a polyurethane adhesive as described, havingdesired mechanical, adhesive, and chemical properties, and may contain abase compound or backbone of an oligomer, polymer, or prepolymer of anydesired chemistry, such as aliphatic, aromatic, polyether, polyester,etc. Exemplary polyols include polyether polyols and polyesters. Thepolyol (e.g., monomer, oligomer, or polymer) can be of any molecularweight, e.g., a molecular weight of below about 1,000, such as belowabout 500, 400, or 300.

A useful polyol may preferably contain a high level of di-functionalmonomers, e.g., diols, preferably at least about 90, 95, or 99 percentby weight diols, as opposed to higher-functionality polyols such astriols; i.e., the average functionality of the polyol can be below 3,e.g., below about 2.5, 2.2, or 2.1.

The relative amount of polyol compound to polyisocyanate compound usedto prepare the polyurethane polymer can be any relative amounts that aredetermined to be useful to provide a pressure-sensitive adhesive asdescribed herein, that has useful or advantageous mechanical andadhesive properties as also described, and, therefore, may be useful orespecially useful in a step of lapping a microelectronic devicesubstrate. In certain preferred examples of polyurethane adhesives, thepolyurethane polymer can contain relative amounts of polyisocyanatecompound to polyol compound in a range from 1:1 to 2:3, i.e., from 40 to50 parts by weight polyisocyanate compound, and from 50 to 60 parts byweight polyol compound, based on 100 parts by weight totalpolyisocyanate and polyol compounds.

The reaction of the di-isocyanate and the polyol can be performed in thepresence of a catalyst, with heat curing (activation), or both, toproduce the polyurethane polymer from the polyisocyanate and polyolcompounds. Preferred polyurethanes, if polymerized by use of a catalyst,can be prepared using a catalyst that does not contain tin (i.e., anon-tin catalyst), such as a bismuth-based catalyst, e.g., bismuthcarboxylate. Accordingly, preferred polyurethane adhesives are “free oftin,” meaning, for example, that the adhesive does not contain asubstantial amount of tin as a catalyst and preferably contains lessthan 1 part per million (ppm), e.g., less than 0.5 or 0.1 ppm tin basedon total weight polyurethane adhesive material.

Useful polyacrylate adhesives can be formed by reacting one or acombination of “(meth)acrylate” monomers (the term “(meth)acrylate”referring collectively to acrylate and methacrylate monomers), to form apolymer, which may be a homopolymer or a copolymer. The monomers can beas desired and useful to form a polyacrylate adhesive having propertiesas described herein, with useful example including methylmethacrylate(MMA), ethyl acrylate (EA), butyl acrylate (BA),hydroxyethylmethacrylate (HEMA), and 1,3-budanediol dimethacrylate(BDDMA).

According to one adhesive embodiment, the polyacrylate adhesive can be ahomopolymer of methylmethacrylate, i.e., poly(methylmethacrylate), e.g.,can prepared exclusively or nearly exclusively from methylmethacrylatemonomers, such as by polymerizing monomer that includes at least 99,99.5, or 99.9 percent by weight methylmethacrylate monomers.

According to other preferred embodiments, the polyacrylate can be acopolymer of methylmethacrylate and one or more other acrylate ormethacrylate comonomers. The comonomer can by any useful monomer, withexamples including ethyl acrylate (EA), butyl acrylate (BA),hydroxyethylmethacrylate (HEMA), 1,3-budanediol dimethacrylate (BDDMA),and combinations thereof. A copolymer of methylmethacrylate can contain,for example, from about 50 to 95 parts by weight methylmethacrylate withfrom 5 to 50 parts by weight (meth)acrylate comonomers, based on totalweight copolymer. Example copolymer can contain the methylmethacrylatemonomer in combination with one or more of: from 1 to 10, e.g., from 1to 5 parts by weight ethyl acrylate (EA); from 1 to 10, e.g., from 1 to5 parts by weight butyl acrylate (BA); from 1 to 10, e.g., from 1 to 5parts by weight hydroxyethylmethacrylate (HEMA); from 1 to 10, e.g.,from 1 to 5 parts by weight 1,3-budanediol dimethacrylate (BDDMA), ortwo or more of these comonomers in an amount as specified. Exampleadhesives can be prepared using these monomers, as specified, in theabsence or the substantial absence of other monomers, and in thesubstantial absence of a crosslinking agent such as a poly-functional(meth)acrylate compound that contains 2, 3, or more moieties that arereactive with the (meth)acrylate monomers, e.g., 2, 3, or more reactive(meth)acrylate moieties; such adhesives may contain, e.g., less than 1,0.5, or 0.1 weight percent of multi-functional (e.g.,multi-(meth)acrylate-functional) crosslinking agent.

Preferred adhesives (e.g., polyacrylate or polyurethane) can contain amajor amount of the polyacrylate or polyurethane adhesive polymer, suchas an amount that is at least 60, 70, 80, 90, or 95 percent by weight ofthe polyacrylate or polyurethane polymer, based on total weightadhesive. Optionally, though, as desired, one or more of a plasticizer,a tackifier, or both, may also be included in the adhesive.

A plasticizer is an additive that is chemically different from theadhesive polymer of a pressure-sensitive adhesive composition, and thatincreases the plasticity or fluidity of a material, e.g.,pressure-sensitive adhesive. According to the invention, plasticizer maybe added to achieve a desired fluidity and flexibility of the adhesive,to result in mechanical properties (e.g., modulus, tan delta) asdescribed, thereby being useful or especially useful in a kiss lappingstep as described. Many examples of plasticizers are known in theadhesive arts. Many common plasticizers are based on esters ofcarboxylic acids with linear or branched aliphatic alcohols of moderatechain length. Phthalate esters of straight-chain and branched-chainalkyl alcohols are common plasticizers. Other examples include oilesters such as a methyl or ethyl soybean oil ester, which are well knownand commercially available from multiple sources. If present, aplasticizer may be present in an amount that has a desired effect on aproperty of the adhesive such as elastic modulus, loss modulus, or tandelta, example amounts being up to about 20, 10, or 5 weight percentplasticizer based on total weight adhesive.

A tackifier or “tackifier resin” is a material that can be added to apressure-sensitive adhesive to promote adhesion and tack. Many examplesof tackifying resins are known in the pressure-sensitive adhesive arts,the different types having different chemistries, different physicalproperties such as softening point, ranges of molecular weights andmolecular weight distributions, and effective levels of tack or adhesionpromotion. Example tackifier resins include both natural and modifiedresins, polyterpene resins, phenol-modified hydrocarbon resins,aliphatic and aromatic hydrocarbon resins, hydrogenated hydrocarbons,hydrogenated resins, and hydrogenated resin esters and rosins, amongothers. A tackifier, if present in an adhesive as described, may beincluded in an amount that results in a desired level of tack, adhesion,or both, at a surface of the pressure-sensitive adhesive, with exampleamounts being up to about 30, 20, 10, or 5 weight percent based on totalweight adhesive.

An adhesive as described can be prepared and handled during use in anyconvenient fashion. Typically, for use in a lapping step as described,the adhesive should be in the form of a thin, preferably (but notnecessarily) continuous layer of the polymerized adhesive material thatcan be placed between a flat surface of a substrate such as a sliderbar, and a flat surface of a carrier. To provide for convenience of usewhen handling and placing a layer of the adhesive between a surface of asubstrate and a surface of a carrier, the adhesive can be placed incontact with a release liner (or “transfer liner” or simply “liner”),which can be a flat film of material that can be useful to receive afilm of the adhesive layer, and from which the adhesive layer can beeasily and readily removed. Also, optionally, for convenience, anadhesive as described can be part of an adhesive “stack” that includesthe adhesive, a release liner placed against one surface of theadhesive, and one or more additional layers such as a base layer on theside of the adhesive opposite of the release liner, a second adhesive(e.g., on the base layer on a side opposite of the adhesive material),and a second release liner in contact with a surface of the secondadhesive.

FIG. 1 shows an example of an adhesive stack that includes adhesive asdescribed herein, and that can be conveniently used in a lapping step asdescribed. Referring to FIG. 1, stack 10 includes release liner 2,adhesive layer 4, base layer 6, second adhesive 8, and second releaseliner 12. Adhesive layer 4 is an adhesive material as described herein,containing a major amount of non-silicone-based pressure-sensitiveadhesive, such as a polyurethane adhesive or a polyacrylate adhesive.Second adhesive 8 can be any adhesive that is effective to securely holdto a surface of a carrier during a lapping step. Examples of usefulsecond adhesives include polyacrylate pressure-sensitive adhesives,especially high strength, organic solvent-containing polyacrylatepressure-sensitive adhesives.

Each release liner 2 and release liner 12 may be a polymeric film thatis coated on one major surface (the surface facing adhesive 4 oradhesive 8) with a release material (e.g., a silicone material) thatwill be releasable from, i.e., have low adhesion to, pressure-sensitiveadhesive 4 or pressure-sensitive adhesive 8, respectively. Examples ofpolymeric films that can be coated with a release material, such assilicone, include temperature stable plastic films such as: polyesterfilms, e.g., poly(ethylene terephthalate) (PET) films, poly(ethylenenaphthalate) (PEN) film, and poly(butylene terephthalate) (PBT) films;olefinic films prepared from one or more α-olefins as monomercomponents, such as polyethylene (PE) films, polypropylene (PPs) films,polymethylpentene (PMP) films, ethylene-propylene copolymer films, andethylene-vinyl acetate copolymer (EVA) films; poly(vinyl chloride) (PVC)films; vinyl acetate resin films; polycarbonate (PC) films; amongothers.

Base layer 6 may be made of any one or more of these materials, but doesnot include a release material at a surface and instead includes asurface that is adapted (e.g., primed) to receive and strongly adhere toadhesive 4 and second adhesive 8.

For use in a lapping step as described, a preferred thickness of stack10, meaning the total thickness all of the release liner 2, adhesivelayer 4, base layer 6, second adhesive 8, and second release liner 12,combined, can be in a range from about 25 to 35 mils, e.g., from 25 to30 mils, or from 26 to 28 mils. A preferred thickness for adhesive layer4 can be in a range from about 14 to 21 mils, e.g., from 15 to 20 mils.Thicknesses of release liner 2, base layer 6, second adhesive 8, andsecond release liner 12 can be in ranges useful to allow for a desiredtotal thickness of stack 10, with each of these layers being in a rangefrom 1 to about 10 mil, e.g., about 2, 3, or 5 mil.

In use, the adhesives of stack 10 can be applied to a carrier by anyorder of steps that include removing the release liner 2, applyingadhesive layer 4 to a surface of a substrate (opposite of a “contacted”surface of a lapping step), removing release liner 12, and applyingadhesive layer 8 to a surface of a carrier, to produce a configurationas illustrated at FIG. 3, which shows adhesive layer 8 bonded on one ofits surfaces to a surface of carrier 22 and being bonded on a secondsurface to base layer 6, and adhesive layer 4 being bonded on onesurface to a surface of substrate 24 and being bonded on a secondsurface to base layer 6. Note that adhesive layer 4 need not be indirect contact with the surface of the carrier, but may optionally beadhered indirectly to, or non-directly placed or located on, the surfacethrough one or more additional layers, such as another adhesive layer(e.g., second adhesive 8), a base layer (6) of the described stack 10,or both.

According to methods of the invention, an elastomeric pressure-sensitiveadhesive as described, which is non-silicone-based, can be used in alapping step, e.g., a final lapping step or a “kiss lapping” step, forthe purpose of securing a microelectronic device substrate to a carrier,to hold the substrate to a surface of the carrier during the lappingstep. The lapping step can be designed to accomplish one or twoimportant objectives. A first objective can be to remove an amount ofmaterial from a surface of the substrate to produce a desired thicknessof a layer of the surface material, such as to produce a desired stripeheight between a surface of a slider assembly and one or more transducerheads located below the surface of the slider assembly. A secondpossible objective is, by removal of the surface layer material, toproduce a desired shape of a surface of the substrate, for example adesired shape of a surface of a slider element of a slider assembly.

A lapping process may be a multiple step process, beginning with aninitial removal step, often called a “rough lapping” step, and endingwith a polishing step, often called “kiss lapping” or “polishinglapping” step. The rough lapping step, or a combination of two or morerough lapping steps, may be performed to remove as much as 20 microns ofmaterial from a substrate surface, such as from a surface of a sliderbar. The kiss lapping step is a final polishing and a precision shapingstep. Kiss lapping is less aggressive in its removal of material fromthe substrate as compared to a rough lapping step or steps. A kisslapping step may typically result in removal of not more than 100nanometers of material from the substrate surface, e.g., at a locationof a stripe height measurement. A kiss lapping step requires flexiblemounting of the substrate to the carrier, to achieve desired globalshaping of the slider element of a slider assembly during the lappingstep. Accordingly, pressure-sensitive adhesives having mechanicalproperties as described herein can be useful in the kiss lapping step ofa slider assembly, to result in desired global shaping of the sliderelement of the slider assembly, in addition to a desire amount ofremoval of surface layer material covering one or more transducer headsat an end of the slider assembly (measured as “stripe height”), that endbeing the “trailing end” of the slider assembly during the lapping stepas the slider assembly contacts the abrasive material, with relativemotion.

An example of a substrate 24 (see FIGS. 2 and 3) is a slider bar, whichincludes a contacted surface or surface layer made of a combination ofaluminum oxide (Al₂O₃) and titanium carbide (TiC). At the start of afinal lapping step, the thickness of the surface layer has previouslybeen reduced by a rough lapping step. During the kiss lapping step, theamount of the material (e.g., aluminum oxide (Al₂O₃) and titaniumcarbide (TiC)) that is removed from the surface layer, e.g., at alocation of a stripe height, will usually be an amount that is less thanabout 100 nanometers, for example from about 5 to about 80 nanometers ofmaterial, or from about 10 to about 30, 40, 50, or 60 nanometers ofmaterial.

Referring now to FIG. 2, schematically depicted is a lapping system usedfor a kiss lapping step of a substrate, for example a slider bar. To anactuator or fixture 20 is operably connected carrier 22, to which ismounted slider bar 24 (or another substrate), by adhesive stack 10 (seeFIG. 1) (not including release liners 2 and 12). One surface (contactedsurface) of substrate (e.g., slider bar) 24 is illustrated as contactinga moving abrasive surface (the upper surface) of lapping plate 26 (alsooften referred to as a platen). Adhesive stack 10 includes adhesive 4,which is secured to substrate 24, and adhesive 8, which is secured to asurface of carrier 22. Adhesive stack 10 also includes base layer 6,which is located and adhesively held between adhesive 4 and adhesive 8.

Not shown in FIG. 2, present on the upper surface of lapping plate 26,are abrasive particles or an abrasive surface, to make up an abrasivematerial for contacting the contacted surface of substrate 24. Theabrasive particles or surface may be present in a slurry or may be fixedto the surface of lapping plate 26, for example by adhesive or byelectroplate. Also typically present at the surface of lapping plate 26is a lubricant such as an oil, e.g., mineral oil. In use, lapping plate26 is rotated relative to slider bar 24, which can remain stationary.One surface (the “contacted surface”) of slider bar 24 is held incontact with the moving abrasive material surface of lapping plate 26with a desired amount of pressure (e.g., less than 25 pounds per squareinch, such as from about 5 to about 20 pounds per square inch). Theabrading action caused by the moving abrasive material removes materialfrom the contacted surface of slider bar 24, e.g., to result in adesired stripe height and to also provide a desired shape of thecontacted surface.

Referring now to FIG. 3, an embodiment of an exemplary carrier 22 isillustrated, having secured thereto substrate (e.g., slider bar) 24 byuse of adhesive stack 10 placed between a surface of carrier 22 and thebackside surface of substrate 24. Carrier 22 includes a base 28, formounting carrier 22 to fixture 20. Base 28 is a rigid base, typicallymade of material such as metal, glass, polymer, or ceramic. Base 28 maybe a single-piece or a multiple-piece fixture, and may include anynumber of optional features such as pliable fingers or nodes (see forexample, U.S. Pat. No. 8,066,547 to Schuh et al.), actuation pointsalong the length of carrier 22 (see for example, U.S. Pat. No. 6,475,064to Hao et al.), and other elements designed to improve, affect, orcontrol one or more the dimensions or the shape of the contacted surfaceof a substrate such as slider assemblies of slider bar 24 during thelapping process. Base 28 may have incorporated therewith circuitry(e.g., flexible circuitry) for monitoring an amount of material removedfrom a substrate, e.g., at a stripe height of individual sliderassemblies of a slider bar 24, or of groups of adjacent sliderassemblies of slider bar 24.

More generally, according to certain lapping methods, a contactedsurface of a slider bar or other substrate is lapped by use of a lappingmachine, e.g., as illustrated, with motion (e.g., rotating motion) ofthe abrasive material and contact of the abrasive material with thecontacted surface of the substrate while the substrate is held at thesurface of the carrier. For lapping of a slider bar, the progress of thelapping step is monitored to achieve a predetermined stripe height forslider assemblies of the slider bar. As the abrasive material contactsthe substrate, it advances from the leading end and middle portion ofthe slider assembly, which contain the slider elements of the sliderassemblies, to the trailing end, which contains the one or moretransducing heads and at which location the stripe height is measured.The stripe height of single slider assemblies on the slider bar may bemonitored, and adjustments may be made to the process to remove more orless material from the trailing end of the slider assembly byapplication of a greater or lesser amount of pressure to one or moreslider assemblies on the slider bar. When the desired stripe height ofthe slider assemblies on the slider bar is achieved, the lapping stepcan be stopped and the lapped slider assemblies can be removed from thecarrier.

According to the invention, including the use of an adhesive as adhesive4 of FIG. 3, having properties described herein, including elasticmodulus and tan delta, the lapping step also achieves a desired shape ofthe slider element of the slider assemblies of the slider bar. Inspecific, these properties allow for an amount of flexibility andelasticity of the adhesive that will produce an amount of movement,i.e., twisting, of the slider bar and its individual slider assemblies,to produce slider elements of the slider assemblies that have desiredglobal shaping.

1-17. (canceled)
 18. Elastomeric adhesive film comprising adhesivepolymer, the adhesive film being useful to adhere a microelectronicdevice substrate to a carrier during a step of lapping a surface of themicroelectronic substrate, the adhesive film having: an elastic modulusin a range from 100 to 500 kilopascals measured at 25 degrees Celsius, aTan Delta in a range from 0.05 to 0.2 measured at 25 degrees Celsius.19. Adhesive film as recited at claim 18 having a shear strength in arange from 50 to 1000 grams.
 20. (canceled)
 21. Adhesive film as recitedat claim 18 comprising: less than 10 weight percent organic solvent,less than 10 percent entrapped gas by volume, or both.
 22. Adhesive filmas recited at claim 18 wherein the adhesive polymer contains at least 90weight percent polyurethane derived from polyisocyanate and polyol,based on total weight adhesive polymer.
 23. Adhesive film recited atclaim 22 wherein the polyurethane is derived from: polyisocyanatecomprising at least 99 weight percent di-isocyanate, based on totalweight polyisocyanate, and polyol comprising at least 99 weight percentdiol, based on total weight polyol.
 24. Adhesive film as recited atclaim 22 wherein the polyisocyanate is an aromatic di-isocyanate and thepolyol is a polyether diol.
 25. Adhesive film as recited at claim 22wherein the polyol is a diol having a molecular weight below about 300.26. Adhesive film as recited at claim 22 wherein the polyurethanepolymer is derived from reactive materials that comprise less than 0.5weight percent crosslinker.
 27. Adhesive film as recited at claim 22wherein the polyurethane is derived from polyisocyanate and polyol inrelative amounts of polyisocyanate to polyol in a range from about 1:1to about 2:3.
 28. Adhesive film as recited at claim 22 wherein theadhesive film contains less than 1 part per million (ppm) tin. 29.Adhesive film as recited at claim 22 wherein the polyurethane isprepared by polymerizing polyisocyanate and polyol in the presence ofbismuth-containing catalyst.
 30. Adhesive film as recited at claim 18,wherein the adhesive polymer contains at least 99 weight percentpoly((meth)acrylate), based on total weight adhesive polymer. 31.Adhesive film as recited at claim 30 wherein the poly((meth)acrylate) isselected from poly(methylmethacrylate) homopolymer, poly((meth)acrylate)copolymer, and combinations thereof.
 32. Adhesive film as recited atclaim 30 wherein the adhesive film comprises at least 70 weight percentpoly(methylmethacrylate) homopolymer, poly((meth)acrylate) copolymer,and combinations thereof.
 33. Adhesive film as recited at claim 30wherein the adhesive film comprises: from 70 to 100 weight percentpoly((meth)acrylate) adhesive polymer, from 0 to 30 weight percenttackifier, and from 0 to 10 weight percent plasticizer, based on totalweight adhesive film.
 34. Adhesive film as recited at claim 33 whereinthe adhesive polymer is derived from reactive materials that containless than 0.5 weight percent reactive monomer having a functionality of3 or more.
 35. An adhesive film stack comprising adhesive film asrecited at claim 18 in contact with a release liner on a first surfaceof the film.
 36. An adhesive film stack as recited at claim 35 whereinthe adhesive film has a thickness in a range from 14 to 21 mils.
 37. Anadhesive film stack as recited at claim 35 comprising: a second adhesivelayer, a base layer between the adhesive film and the second adhesivelayer, and a second release liner in contact with the second adhesivelayer.
 38. An adhesive film stack as recited at claim 37 wherein thesecond adhesive layer comprises an organic solvent-containingpolyacrylate pressure-sensitive adhesive.